Ground deformation at Mt. Etna detected by three GPS surveys carried out in 2004, 2005, and 2006 is analyzed. The data set encompasses the 2004–2005 eruptions and foreruns those of 2006. A wide deflation of the entire volcano was detected from 2004 to 2005, accompanying the 2004–2005 eruption; conversely an evident inflation phase, from 2005 to 2006, followed this eruption and preceded the 2006 one. In both cases, the deflation‐inflation cycle was accompanied by a continuous seaward motion of the eastern flank. We inverted both data sets (2004–2005 deflation and 2005–2006 inflation) using an optimization algorithm based on the Genetic Algorithm (GA) in order to detect the ground deformation sources. The wide contraction measured during the eruption reveals the drainage of a sill‐shaped magma reservoir located by data inversions at a depth of about 4.5 km b.s.l. The pressurizing source modeled for the 2005–2006 time interval indicates a refilling of the shallower near‐vertical plumbing system of the volcano. This could indicate a change in the geometry of the feeding system, active after the 2004–2005 eruption, with a new and shallower magma storage that could have enabled the resumption of volcanic activity that was observed at summit craters in 2006. These results improve the imaging of the plumbing system of Mt. Etna volcano.

[1] A study of the deformation pattern of Mount Etna volcano based on the results from the Permanent Scatterers (PS) technique is reported. Ground motion data provided by the interferometric synthetic aperture radar (InSAR) PS technique from 1995 to 2000 are compared and validated by GPS data. An analysis of the ascending and descending line of sight (LOS) components of ground velocities has yielded detailed ground deformation maps and cross sections. This analysis allows detection and constraint of discontinuities in the surface velocity field. LOS velocities have then been combined to calculate the vertical and horizontal (E-W) ground velocities. A wide inflation of the edifice has been detected on the western and northern flanks (over an area of about 350 km 2 ). A seaward motion of the eastern and southern flanks has also been measured. PS data allows the geometry and kinematics of the several blocks composing the unstable flanks to be defined even in the highly urbanized areas, and their displacement rates have been measured with millimeter precision. This analysis reveals the extension of some features beyond their field evidences and defines new important features. The results of this work depict a new comprehensive kinematic model of the volcano highlighting the gravitational reorganization of the unbuttressed volcanic pile on its slippery clay basement on the southern flank, but an additional drag force due to a strong subsidence of the continental margin facing the Etna volcano is necessary to explain the PS velocity field observed on the eastern flank.Components: 10,900 words, 6 figures.

After the end of the 2002–2003 eruption, Mount Etna activity was characterized only by gentle degassing at the summit craters and some earthquake swarms. Suddenly, an eruption started on 7 September 2004 in complete absence of summit crater volcanic activity, seismicity or seismic tremor, and ground deformation. This is the first time that magma poured out passively without preeruptive and coeruptive volcanic and/or geophysical phenomena. The primary key to understanding this event is represented by the ground deformation pattern recorded through GPS measurements during the year before the eruption. The ground deformation shows inflation superimposed by a predominant eastward movement of the eastern sector at a rate never observed before in a noneruptive period. The images from satellite radar interferometry confirmed this pattern. The deformation field clearly shows that the maximum tension in the eastern sector of the volcano caused the opening of the eruptive fracture which favored the silent pouring out of already resident magma.

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Ground deformation data from GPS and differential synthetic aperture radar interferometry (DInSAR) techniques are analyzed to study the July–August 2001 Mount Etna eruption as well as the dynamics preceding and following this event. Five GPS surveys were carried out on the entire Mount Etna network or on its southeastern part, from July 2000 to October 2001. Five ERS-2 ascending passes and three descending ones are used to form five interferograms spanning periods from a month to 1 year, before and encompassing the eruption. Numerical and analytical inversions of the GPS and DInSAR data were performed to obtain analytical models for preeruptive, syneruptive and posteruptive periods. The deformation sources obtained were from the Mogi model: (1) pressure sources located beneath the upper western flank of the volcano, inflating before the eruption onset and deflating afterward; (2) tensile dislocations to model the intrusion of a N-S dike in the central part of the volcano; and (3) two sliding and two normal dislocations to model the eastern and southern flank dynamics. This study confirms that the lower vents of the eruption were fed by a magma stored at depth ranging from 9 to 4 km below sea level, as proposed from petrochemical and geophysical researches. The rising of the magma through the shallow crust started months before the eruption onset but accelerated on the last day; this study suggests that in the volcanic pile the path of the rising magma was driven by the volcano topography. The eastern sliding plane and the interaction between dike intrusion and flank instability have been better defined with respect to previous studies. The sliding motion abruptly accelerated with the dike intrusion, and this continued after the end of the eruption. The acceleration was accompanied by the propagation of the strain field toward the eastern periphery of the volcano